Condensed Matter Seminar - Andrew Sachrajda, The National Research Council - Coherent Behaviour in a Triple Quantum Dot Circuit

In this talk I will describe our experimental investigations of an AlGaAs/GaAs based triple quantum dot circuit and their comparison with theoretical models. We are able to employ both quantum transport and charge detection down to single electron/spin occupation and employ many of the pulsing techniques developed previously for two dot circuits. Our particular focus is the (1,1,1) regime in which a single spin occupies each quantum dot. By varying pulse parameters we are able to observe coherent behaviour between specific three-spin levels including the DiVincenzo all-exchange qubit and various manifestations of Landau-Zener -Stückelberg oscillations and their interplay. I will demonstrate the triple quantum dot equivalent of the double quantum dot Pauli blockade effect and show how in a linear triple quantum dot leakage currents can occur directly between edge dots via coherent quantum superpositions where the occupation of the center dot remains fixed. Finally I will demonstrate a quantum backaction process mediated via single phonon interferometry. The figure below shows experimental LZS oscillations and the device layout used.